1. Field of the Invention
The present invention relates to an aqueous fine particle dispersion comprising a dispersible polymer having a specific structure and an oil-soluble dye, an ink composition comprising the fine particle dispersion, and an ink-jet recording method using the ink composition.
2. Description of the Related Art
As use of computers has become widespread in recent years, ink-jet printers have become to be widely used not only in offices but also in homes for printing on paper, film and cloth. Oil-based inks, aqueous inks and solid inks are well-known as ink-jet recording inks, and aqueous inks are particularly advantageous in terms of easiness of production, ease of handling, low odor-generating properties and high safety. Further, aqueous inks are the type of ink predominantly used.
The majority of aqueous inks have advantages such as high transparency and high color density since water-soluble dye, which is dissolved in a molecular state, is used therein. However, because such dye is water-soluble, the aqueous inks suffer from disadvantages such as poor water resistance, a tendency to bleed when printing on paper thus significantly deteriorating print quality, and poor light fastness. Further, significant deterioration in preservability of images occurs, due to the influence of oxidizing gases (SOx, NOx, ozone etc.) on recording paper (hereinafter, also referred to as photo quality paper) provided thereon with an inorganic fine particle-containing porous ink-receiving layer.
Aqueous inks using pigments or dispersible dyes have been proposed in order to solve the problems described above (see Japanese Patent Application Laid-Open (JP-A) No. 56-157468).
However, although the water resistance of such aqueous inks is improved to a certain extent, it is not improved to a satisfactory degree and problems remain such as poor storage stability of pigments or disperse dyes dispersed in such as aqueous inks and a tendency for ink discharging openings clog easily. Further, the problem exists that inks using a pigment or a dispersible dye have poor permeability into photo quality paper, and the pigment or dye is easily removed from the surface when rubbed by a hand.
On the other hand, a method of incorporating an oil-soluble dye into a polymer has been proposed (see, for example, JP-A Nos. 58-45272 and JP-A 62-241901). However, the ink-jet ink obtained by this method is poor in tone and inferior in color reproducibility, and particularly poor in image durability against oxidizing gases and in rubbing resistance when printing on photo quality paper.
An ink provided with excellent coloration and rubbing resistance by introducing a salt-forming group and a polyalkylene oxide group to a polymer has been proposed (see, for example, JP-A No. 2001-123097), which has excellent rubbing resistance against rubbing with fingers, but is poor in high-level rubbing resistance against rubbing with an eraser.
Additionally a method of improving tone and rubbing resistance by using a high-boiling point organic solvent and a dye has been proposed (see, for example, JP-A No. 2001-262018), but the improvement is insufficient in cases where high-leveled image durability is required.
As described above, an ink composition containing a fine particle dispersion that is easy to handle and has low odor-generating and high safety properties; wherein the particle size of the dispersion particles is small and the dispersion has superior dispersion stability and storage stability such that when the particle dispersion is applied to ink the ink is free from clogging at the end of a nozzle and has superior discharge stability; which has superior coloration and tone (hue) regardless of the type of paper used; which has superior ink permeability even when using the photo quality paper mentioned above; which has superior water resistance after printing, particularly superior image preservability (in particular, light fastness and ozone resistance) and superior rubbing resistance; and which enables high quality printing at high density, has not yet been provided.